As silicon semiconductors, a single crystalline silicon semiconductor, a polycrystalline silicon semiconductor, and an amorphous silicon semiconductor may be exemplified. Among these various silicon semiconductors, the polycrystalline silicon semiconductor is widely used as a material for a semiconductor element using a silicon semiconductor since the polycrystalline silicon semiconductor is easy to manufacture as compared to the single crystalline silicon semiconductor.
A pin diode is an example of a semiconductor element that uses the polycrystalline silicon semiconductor. The pin diode refers to a semiconductor element having a pin structure in which an i-type (non-doped) polycrystalline silicon layer with a high electric resistance is disposed between a p-type polycrystalline silicon layer and an n-type polycrystalline silicon layer. The pin diode is obtained, for example, by forming a p-type polycrystalline silicon layer doped with boron on a base body including an electrode layer, forming an i-type polycrystalline silicon layer on the p-type polycrystalline silicon layer, and Miming an n-type polycrystalline silicon layer doped with phosphorus on the i-type polycrystalline silicon layer.
There are two methods known for forming a polycrystalline silicon layer. The first method is to grow the polycrystalline silicon layer using a thermal CVD method in which a temperature condition is about 600° C. An example of this method is disclosed as a first exemplary embodiment in Patent Document 1. The second method is to obtain the polycrystalline silicon layer by forming an amorphous silicon layer and applying thermal annealing to the amorphous silicon layer. An example of this method is disclosed as a second exemplary embodiment in Patent Document 1. In addition, Patent Document 2 discloses a method using laser annealing instead of the thermal annealing.